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DLATRSRun Method

Purpose ======= DLATRS solves one of the triangular systems A *x = s*b or A'*x = s*b with scaling to prevent overflow. Here A is an upper or lower triangular matrix, A' denotes the transpose of A, x and b are n-element vectors, and s is a scaling factor, usually less than or equal to 1, chosen so that the components of x will be less than the overflow threshold. If the unscaled problem will not cause overflow, the Level 2 BLAS routine DTRSV is called. If the matrix A is singular (A(j,j) = 0 for some j), then s is set to 0 and a non-trivial solution to A*x = 0 is returned.

Namespace: DotNumerics.LinearAlgebra.CSLapack
Assembly: DWSIM.MathOps.DotNumerics (in DWSIM.MathOps.DotNumerics.dll) Version: 1.0.0.0 (1.0.0.0)
Syntax
Copy
public void Run(
	string UPLO,
	string TRANS,
	string DIAG,
	string NORMIN,
	int N,
	double[] A,
	int offset_a,
	int LDA,
	ref double[] X,
	int offset_x,
	ref double SCALE,
	ref double[] CNORM,
	int offset_cnorm,
	ref int INFO
)
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Parameters

UPLO  String
(input) CHARACTER*1 Specifies whether the matrix A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular
TRANS  String
(input) CHARACTER*1 Specifies the operation applied to A. = 'N': Solve A * x = s*b (No transpose) = 'T': Solve A'* x = s*b (Transpose) = 'C': Solve A'* x = s*b (Conjugate transpose = Transpose)
DIAG  String
(input) CHARACTER*1 Specifies whether or not the matrix A is unit triangular. = 'N': Non-unit triangular = 'U': Unit triangular
NORMIN  String
(input) CHARACTER*1 Specifies whether CNORM has been set or not. = 'Y': CNORM contains the column norms on entry = 'N': CNORM is not set on entry. On exit, the norms will be computed and stored in CNORM.
N  Int32
(input) INTEGER The order of the matrix A. N .GE. 0.
A  Double
*x = s*b or A'*x = s*b
offset_a  Int32
 
LDA  Int32
(input) INTEGER The leading dimension of the array A. LDA .GE. max (1,N).
X  Double
(input/output) DOUBLE PRECISION array, dimension (N) On entry, the right hand side b of the triangular system. On exit, X is overwritten by the solution vector x.
offset_x  Int32
 
SCALE  Double
(output) DOUBLE PRECISION The scaling factor s for the triangular system A * x = s*b or A'* x = s*b. If SCALE = 0, the matrix A is singular or badly scaled, and the vector x is an exact or approximate solution to A*x = 0.
CNORM  Double
(input or output) DOUBLE PRECISION array, dimension (N) If NORMIN = 'Y', CNORM is an input argument and CNORM(j) contains the norm of the off-diagonal part of the j-th column of A. If TRANS = 'N', CNORM(j) must be greater than or equal to the infinity-norm, and if TRANS = 'T' or 'C', CNORM(j) must be greater than or equal to the 1-norm. If NORMIN = 'N', CNORM is an output argument and CNORM(j) returns the 1-norm of the offdiagonal part of the j-th column of A.
offset_cnorm  Int32
 
INFO  Int32
(output) INTEGER = 0: successful exit .LT. 0: if INFO = -k, the k-th argument had an illegal value
See Also